1. Field of the Invention
The invention relates generally to broadcast television systems and more particularly to a system and method for recording pushed data content broadcast in an interactive television system.
2. Description of Related Art
Interactive television systems provide a means to deliver interactive content as well as ordinary television audio and video to a large number of subscribers. Programs broadcast by these systems may incorporate television audio and video, still images, text, interactive graphics and applications, and many other components. The interactive content of the interactive television signal may therefore include application code, data associated with the audio and video, control signals, raw data and many other types of information. Both the interactive content and the audio and video data are delivered to subscribers as “pushed” data. That is, the data is delivered to each of the subscribers, regardless of whether or not the subscribers requested the data.
Interactive content such as application code or information relating to television programs is usually broadcast in a repeating format. In other words, each piece of information is broadcast a first time, then each is transmitted a second time, and so on. The cycle is repeated so that each piece of interactive data is transmitted, for example, every ten seconds. The pieces of information which are broadcast in this manner form what is referred to as a “carousel.” The sequence of information that makes up the carousel can be prepared in advance, or it can be determined “on the fly.” In one embodiment, a carousel refers to a bundle of data objects coming from a single data producer source. It should be noted that the content of a particular carousel may change over time. For example, changes in carousel content may be due to updates by a data producer source. Frequently, a single carousel is transported as a contiguous data stream. However, it is also possible to multiplex two or more carousels in a single data stream.
Broadcast systems (e.g., interactive television systems) transmit information in a carousel format in order to allow receivers in the system to selectively obtain particular pieces of information in the carousel without requiring a return path from the receivers to the server. If a particular receiver needs a particular piece of information, it can simply wait until next time that piece of information is broadcast, and then extract the information from the broadcast data stream. (If the information were not cyclically broadcast, the receiver would have to transmit a request for the information to the server, thus requiring a return path.) Other receivers in the system can operate in the same manner, each receiver waiting for the information it needs, and then using only that information. By employing carousels to broadcast information, the system eliminates the need to connect each of the receivers with the server and further eliminates the need for the server to process individual requests for information. Generally, a broadcast signal may include a number of programs which in turn may include a number of audio/video streams and/or data streams. Data streams may be used to carry data such as interactive application data, subtitle information, or other data.
The pieces of information, or data objects, in a carousel may be intended to be combined in a single object data stream to form a program. This program may also contain streaming data such as audio or video. For example, an interactive television game show may combine television audio and video with interactive content such as application code which allows users to answer questions. Another example would be a news program which combines audio and video with application code that inserts current stock prices in a banner at the bottom of the screen. (It should be noted that many types of programs are possible, and it is not necessary to include either audio, video or interactive content any particular program. A program might contain only audio and interactive data (e.g., an interactive radio program,) or it might contain only interactive data (e.g., an interactive weather program that does not contain audio or video streams.) Typically, each program is associated with a corresponding channel and, when a channel containing a particular program is selected by the interactive television receiver, the data which is being broadcast on that channel is downloaded and the program is started.
The programs broadcast by the interactive television system may include components (data objects) that reference and interact with each other in a manner similar to that of DVD programs or SMIL pages. DVD programs may, for example, access different data objects which allow customized playback of a program. The program may be customized to use specific languages, to skip certain portions of the program (e.g., skipping scenes of video based on parental controls,) to display specific menus, etc. SMIL is a markup language that allows different multimedia objects to be integrated into a single presentation. SMIL pages may reference objects in data streams, manipulate these objects, synchronize data streams, etc.
Program content received in a broadcast system is normally intended to be consumed immediately. It is nevertheless possible to record this content for later playback. However the recording of the broadcast information is generally limited to recording that portion of the pushed data stream that was intended to be consumed immediately. While the received information may be re-formatted or re-packetized, it is stored just as it is received—as a stream of data. Because the program may consist of data objects that interact with each other, recording the program as a stream of data may have a number of disadvantages. For example, if the program references “live” data such as stock quotes, this data will be obsolete when the program is replayed. Further, if the program data stream is recorded as is, it may be difficult or even impossible to maintain the synchronicity and interactivity between the different components of the program.